I think BNB is the fastest growing coin it has support from Binance which is number 1 exchange also it has regular coin burns which regularly pump their prices. Also I am pretty sure that BTC will also be above 10k mark. We are in a bull run it's just that BTC is giving a correction to us which is why we are currently hanging around otherwise 10k is pretty clear we don't have any major resistances in between. Also thing is that if BTC increases all coins increases.
BNB
was one of the fastest-growing coins, with a peak 6 months ago. It's still a pretty good and stable investment, but definitely not the fastest-growing one.
From the big names, IMO Tron has the biggest potential to grow now, along with Gramm (when they start it for real).
If you like to speculate, Chainlink is current on a very fast bull run.